Pole-surrounding soil-reinforcing structure



Feb. 19, 1963 J. o. OSTERBERG 3,077,704

POLE-SURROUNDING SOIL-REINFORCING STRUCTURE Filed Sept. 3, 1959 2 Sheets-Sheet 1 FIG. 4 12 FIG. FIG. 8 FIQQ I 51 fi/gg wv /SP1 6P2 16 55 FIG. F l6. l5

W INVENTOR.

I l Jon-1 O. OSTERBERG SP3, 5 7 M'M 36 ATTORNEYS J10. OSTERBERG 3,077,704 POLE-SURROUNDING SOIL-REINFORCING STRUCTURE 2 Sheets-Sheet 2 It! liifvlillltlliii Feb. 19, 1963 Filed Sept. 3, 1959 INVENTOR. v Jom QOSTERBERG BY 1 ;Gw M

ATToZEvs I v-e United States Patent Gfiice 3,077,704 Patented Feb. 19, 1963 This invention relates to poles, posts, and the like, which are installed in the usual upright position with the lower end imbedded in the ground, or rather in the soil thereof, and its object is to provide simple and economical structures and procedures for maintaining the poles, posts, and the like more stably in installed position against side thrusts or forces tending to tip them by accomplishing a partial rotation of the imbedded portion.

Heretofore, many propping, guying, and reinforcing provisions have been adopted to maintain installed soilimbedded poles, posts, and the like (hereinafter usually termed poles), in their normal upright installed position against lateral forces and stresses tending to rot-ate the imbedded portion thereof toward horizontal position by forcing the soil in which they are imbedded to yield. For example, high or gusty winds, heavy wire loads, casual contact by moving vehicles, and other forces below polebreakage values tend to rotate mounted poles from the vertical position toward the horizontal.

One common pole-steadying expedient is to install the pole in an oversize dug or bored hole and to fill the hole space surrounding the pole with poured concrete, and supporting the pole by props or guys until it sets. Among the objections to this procedure are the increased time and expense of installation, and the great tendency for the hardened concrete'to retain and to conduct moisture to the pole to cause rapid deterioration of wood poles and to cause rapid rusting of steel poles, as well as making more difiicult and expensive the task of replacing a pole which has failed through the passage of time or by being broken.

Pole-steadying guy wires, propping poles, and the like are quite expensive and have the further disadvantage that room is often not available for their installation as when the pole is near a roadway or a building. These disadvantages limit their use for power and communication-line poles to certain corner or terminal pole locations.

Further expedients have included employing anchoring apparatus soil-imbedded in surrounding relationship to an installed pole and rigidly connected to the pole by either a disk-like cap member or a spoke-like arrangement. These expedients are expensive, are practically limited to accurately sized steel poles, and cannot be applied readily to existing installed wire-carrying poles.

According to the invention, the foregoing and other difficulties of the structures heretofore proposed are overcome by surrounding an installed pole by a simple groundreinforcing (or soil-reinforcing) structure in the form of a soil-reinforcing band, which is related in diameter to the diameter of the pole, is imbedded in undisturbed ground or soil, and which does not require an imbedded length of more than a relatively small portion of the imbedded depth of the pole.

Further according to the invention, the improved structure may comprise a band composed of twoor more band segments to permit the band to be readily assembled around an installed pole (either newly installed or a previously installed one requiring ground reinforcement), as well as permitting the installation of the segmented band by driving the segments singly and successively into the undisturbed soil.

The above mentioned and other objects and features of this invention and the manner of attaining them will become more apparent, and the invention itself will be best understood, .by reference to the following description of an embodiment of the invention taken in conjunction with the accompanying drawings, comprising FIGS. 1 to 21, wherein:

FIGS. 1 to 3 show respectively a top view, a side sectional view, and a fragmentary enlarged top view of an installation of a preferred segmented form of soil-reinforcing band structure according to the invention;

FIGS. 4 and 5 show respectively a top view and an inside profile view of a single segment of the structure of 1 FIGS. 1 to 3;

FIGS. 6 to 8 show respectively a top view, an inside profile view, and a sectional view taken along line 8-8 of FIG. 7 of a modified form of the segment structure of FIGS. 4 and 5;

FIG. 9 shows a sectional View of a modification of the structure of FIGS. '6 to 8;

FIGS. 10 and 11 show respectively a top view and an inside profile view of a further modified form of segment construction;

FIGS. 12 and 13 show respectively a top view and an inside profile view of a still further modified form of segment construction; FIG. 14 shows a top sectional view of two adjoining joined by vertisegments according to FIGS. 12 and 13 cally disposed joining clip;

FIG. 15 is an inside profile view of the joining clip employed in FIG. 14;

FIG. 16 shows a temporarily attachable driving cap for any of the illustrated segments;

- FIGS. 17 and 18 are respectively a top view and a side sectional view of an installation comprising concentric reinforcing bands according to the invention;

FIGS. 19 and 20 are respectively a diagonal view and a top view of the usual soil-installed pole which has been subjected to substantial tipping forces to cause yielding rotation of the imbedded portion thereof; and

FIG. 21 is an explanatory view showing the common variation with depth below soil surface of tipping forces between the pole and the soil in response to an aboveground tipping force.

Tipping Force Distributi0nFIG. 21

forward forces FF in the direction of tipping force TF,

while portion 52 indicates reverse forces RF in the opposite direction to tipping force TF. It will be observed that the forward forces FF acting on the soil have their greatest value at depth D1 below surface S, starting from a zero value at surface S wherethe relatively unpacked and unsupported soil is easily moved. It is clear that the forces met by a tipping tendency of pole P are those forces with which the soil resists displacement or compression by pole movement.

From depth D1 downwardly, forward forces FF decrease in magnitude toward depth D2, whereat they are Zero. Below depth D2, reverse forces RF appear and increase in magnitude to depth D3, being the depth of pole imbedment. As indicated by curve 50, the pole P,

in obeying forces sufiicient to cause some tipping of the imbedded portion thereof, acts asthoughpivoted about a horizontal axis at depth D2 and at right angles to the force directions. Numerous carefully conducted tests of poles imbedded'from 6 to 9 feet, which is the usual imbedment depths for telephone and power-distribution poles 3 of to 18 inches in diameter, show that depth D1 is well above the middle of the imbedded portion of the pole, and that depth D2 is comparatively close to the lower end of. the pole, and is well, below the middle of the imbedded portion.

The force-distribution curve 50 varies, in shape according to the nature of soil in which the pole P is imbedded. As illustrated in FIG. 21, it is approximately that obtained for a pole P which has been set in a dug hole in undisturbed topsoil and clay sub-soil, withthe usual back fill S il Movement Under StressFIGS. 19 and 20 Referring now to FIGS. 19 and 20, a pole P,,imbedded' in the soil to the usual depth and according to the usual practice, is shown as having been subjected to a sufficient above-ground tipping force to the right to cause the pole to tip sufficiently to move the pole perhaps an inch at the soil line, leaving a gap 19 at the left side of the pole.

Repeated similar test tippings of installed poles P have.

quite uniformly caused gap 19 to be accompanied by aligned soil cracks 20 and 21 to appear in the surface of the ground at' right angles. to the direction of the tip. Such experiments have been, conducted as part of a pro.- gram to discover the resistance of conventionally installed poles to poletipping forces. The observed width atthe pole surface of groundcracksllland 21 is on the order of, but usually less than, the distance of ground-level pole movement at: gap-19,.

From. the foregoing and related observations, it was conceivedthat the tipping of aninstalledpole P of FIGS. 19 and 20. responsive to agivenmoment of tipping force might be greatly reduced by so confining a region of the surrounding soil as to inhibit the formation of cracks such as 20 and 21'. Accordingly, a soil-reinforcing band was imbedded in the soil around an installed untipped pole at about the band location BL shown in dotted lines in FIG. 20.-.. This was accomplished by dropping a band over the installed pole, representing about a 24 inch end section of an empty oil drum from which the head portion has been removed, and imbedding that section concentrically about the installed pole. band could not readily be driven into. the undisturbed soil, as a result of which the soil was dug away from the top portion. of the pole to about the outside diameter of the band andpto a depth equal to the width of the band, permitting the band to beforced snugly into place within the side walls of the enlarged dug opening, following which the. spacebetween the installed pole and the band was layer-filled, packed, and tamped. withclaysoil to give it a. strengthsimilar to that of the normal undisturbed; soil. Repeated tests. then showed that the band-reinforced soil tended to retain the pole upright and concentric with the reinforcing band under forces that caused the tipping illustrated inFIGS. 19. and 20, and that the pole could be caused to tip to the illustrated extent only by applyingan though the band-encircled imbedded part had a diameterincreasedtothat of the reinforcing band, installed at band line BL. These and, further tests indicate that'the optimum diameter of .a. soil-reinforcing:band installed at'BL of:.FIG.. 20 dependsupon.the character or strength resist It. was found that the.

the band itself moves too readily. Generally speaking,

the ratio of pole diameter to reinforcing band diameter should be such that the band diameter is not less than one and one-half pole diameters and is not more than three pole diameters.

Satisfactory matched pole and band diametersfor poles of a rangeof common sizes installed in commonly encounteredclay soils are given in the following table:

Band Diam eter, inches I 7 Pole Diameter, incheseases These band diameters are all within the range of from 1.8 to 3 pole diameters.

First Band Structure Embodiment-FIGS. 1 to 5 FIGS. 1 to 5 disclose the first of a series of structural. embodiments of a split or segmented reinforcing band according to the invention. It may be. assumed, for example, that the pole P1 of F163;]. and: 2 has a diameter of 10 inches and that the bandB of FIGS. 1 and 2has a nominal or inside diameter of 24 inches according to the previously given table of relative diameters, leaving radial 7-inch distance between P1 and B, which is .7 of the diameter 0fP1. band separation may be a large fraction of the pole diameter for wood poles imbedded in clay soils, a somewhat smaller fraction forsoftersoils. The width of the band B of the assumed nominal 24-inch diameter may be from 18. to 24 inches, since the depth to which 10-inch poles are commonly set is such that l81to'24inches is substan tially in excess of the maximum-force depth D1 (FIG. 21). It will be understood, of course, thatno harm-results from having band width and its consequent reinforcing depth somewhat. greater, but it is found that further width in- In order to permit the bandB to be readily assembled around the base of antinstalled pole (including both newly installedand long-installed poles), and to be driven readily into the undisturbed soil aroundthe pole for economy of effort and time of installation, the band B is composed'of a number of similar segments S, such as the six segments illustrated in FIG. 1. These segments are-disclosed as comprisingrespective similar lengths of extruded orcontinuously roller or forged material which may eitherbe formed with the desiredindicated band curvature or may have that curvature imparted by a bending or pressing operation after formation of the basic strip, or after the individual segments S are cut therefrom.

Each segment S comprises a sheet-like main portion-2 having an enlarged rod-like male formation4 at one edge thereof and a female channel formation 3 at the other edge-thereof for closely and slidingly-receiving the male edge formation 4 of an adjacent segment 8. The female formation 3 then nearly encircles its engaged male formation 4 as seen best inFIG. 3, with edge portions 5 being separated sufficiently to receive the sheet-like main portion 2 and to permit some angular displacement movement between adjacent segments, as when more or less ofthe segments are employed to provide a somewhat larger or In general, this radial distance of pole to somewhat smaller band than the full circular band indi-' cated in FIG. 1. For example, the normal six-segment band B may be made into a somewhat larger seven-segment band by adding one more segment, or may be made into a smaller five-segment band by omitting one of the segments of FIG. 1. V i

To further facilitate driving the individual segments S into the undisturbed soil, they may be sharpened as by diagonal edge grinding indicated at 6 in FIGS. 2 and 5.

Preferably after the pole P1 (unless already set) has been set securely following the usual procedure, the segments S of the band B are assembled into the band formation of FIGS. 1 and 3 by sliding them endwise of each other into the illustrated male and female engaging relationship around the pole and above ground level. With the assembled bandB concentric with pole P, the segments S are individually driven down into the soil, preferably by driving the segments S only part way in succession as to a depth of two or more inches, and repeating the segment-by-segment driving procedure until all segments have been driven fully into the undisturbed soil. While the segments may remain flush with the soil surface as indicated in FIG. 2, they are preferably driven a few inches below the normal surface of the soil, as by digging or scraping a shallow trench inside and outside the band B, driving the band to the bottom of the trench, and then leveling soil to cover the imbedded band B.

The driving of the individual segments S into the soil may be accomplished in any desired manner, as by using a wooden mall or a rubber hammer, or by employing a separate driving cap 8 (FIG. 16) for each segment.

A practical requirement of the edge formations 3 and 4 is that each-male formation 4 be rather snugly received within its mating female formation 3 to insure that the band diameter cannot be substantially increased by yielding at the segment junctures when a tipping soil-spreading stress is applied to pole P 1.

In FIGS. 1 and 2., the soil enclosed within the band B is referred to as an inner soil IS, while the undisturbed soil lying outside the band B is referred to as the surrounding soil SS. When a horizontal force in any direction is applied to pole P1 of such magnitude as would tend to cause the pole to tip as indicated for pole P of FIGS. 19 and 20, the surrounding soil SS tends to hold the band B stationary and to confine the tipping of the pole P1 to such as will obey the tipping force by compressing that portion of the inner soil IS which is directly within the tipping path of pole P. As previously explained, the tipping movement of the pole P1 responsive to a given tipping force when soil IS can only be compressed by pole tipping, and cannot be bodily moved to produce cracks as at 20 and 21 of FIGS. 19 and 20, is limited to a small fraction of the extent of the pole tipping indicated at 19 in FIGS. 19 and 20 where the surrounding soil is not reinforced. 1

When the magnitude of the tipping force applied to pole P1 is increased sufficiently to produce a tipping on'the order of that indicated in FIGS. 19 and 20, the major portion of the additional tipping movement is accompanied by a movement of the entire band B and its encircled soil IS and a yielding of the in-path surrounding soil SS to the tipping force. Accordingly, for all tipping movements, of the pole P1 of FIGS. 1 and 2 beyond relatively insignificant values, band B causes the pole to behave largely as though the upper portion of its imbedded part has its diameter enlarged to that of the band B. For the common clay soils, the usual well-set wood poles P1 equipped with a band B as described, tend to resist tipping movement to the extent described for the pole P of FIGS. 19 and 20 for most tipping forces within pole-breaking strength.

Second Segment Embodiment-FIGS. 6 to 8 In the structure of FIGS. 6 to 8, reinforcing bands according to FIGS. 1 to may be constructed of modified Segments S1, each of which is similar to the described segments S except for the addition (1) of a curving shovel-point portion SP1 for the sheet structure 12 (corresponding to 2 of FIGS. 1 to 5), and (2) of a drive cap 17 which may comprise a tough steel member folded around the upper edge of sheet portion 12 and welded or otherwise fixed firmly thereto to permit the segment to be driven into hard undisturbed soil as by an ordinary sledge hammer, and without necessarily requiring the temporary use of drive member 8 of FIG. 16 for each segment. Parts 13 to 16 of S1 correspond respectively to parts 3 to 6 of segments S.

Modification of Second Segment Emb0dimentFIG. 9

Third Segment Emb0diment-FIGS. 10 and 11 FIGS. 10 and 11 disclose a segment S3 which may be employed for each of the segments of band B of FIGS. 1 and 2, but so designed that it may be constructed from fiat sheet stock. The main portion of segment S3 comprises sheet-like member 32 having one edge thereof roll formed to provide a male engagement member 34 corresponding to edge formations 4 of FIGS. 1 to 5. At the opposite edge, female formation 33 is provided as by die-forming the edge portion of S3 to provide one prong of the female portion, the other prong of which is provided by Welding a pre-formed sheet strip 38 to sheet portion 32 of S3 in the position illustrated.

Segment S3 is illustrated as having a shovel-like point portion SP3 and a sharpened edge 36, corresponding to items SP1 and 16 of FIGS. 6 to 8 and to SP2 and 26 of FIG. 9.

Fourth Segment Emb0dimentFIGS. 12 to 15 has in-turned edge portions 50 shown as corner-clipped at 51 to facilitate strip 49 being tapped or driven endwise into the installed clamping position shown in FIG. 14. As illustrated in FIG. 14, the two segments S4 are held firmly in contact with each other by inward pressure contact exerted on the inside of the turned-back loop of each segment S4 by the opposed edges of in-turned wings 50 of clip 49. If preferred, the inward width of Wings 44- of the segments may be equal to the inward width of wings 50 of the clamping clip, but tolerance considerations usually dictate that the width of oneset of Wings be somewhat less than the other for certainty of firm contact of a predetermined set. Ifdesired, clips 49may be made of slightly thicker material than that of segments S4, but the use of material of the same thickness for both is ordinarily satisfactory.

For longitudinal stiffness, as many vertical embossings, convolutions, or off-set ribs 43, as desired, may be formed in the main sheet 'portion 42' of S4 to permit comparatively thin sheet material to be employed in the construction of segments S4,.

Driving CapFIG 16' The previously discussed driving cap 8 of FIG. 16, may be used for driving the segments S of band B of FIGS. 1 to 5 as described, in which case the width of channel 9 is such that sheet portion 2 thereof is closely received therein. Drive cap 8 may also be used to drive the segments S1 to S4 of FIGS. 6 to 14, provided that the channel 9, which receives the upper edge portion of the curved segments S1 to S4, has a width and/or outline to closely receive the segment. The longest horizontal dimension of driving member 8 is preferably such that its channel 9 has a length about as indicated for driving member 17 of FIGS. 6 and 7 to thereby encounter practically all of the top surface of the segment. When used with segment S4 of FIGS. 12 and 13, channel 9 of FIG. 16 should have widened portions to receive such vertical strengthening formations 43 as are contained in the segment.

It will be understood of course that, when driving member 8 is employed, it may be convenient to fit a separate such driving cap atop each segment of the band to avoid having to transfer the cap member from segment to segment during the-described driving operation.

As shown, driving cap 8 has sloping end walls and a flat-topped intermediate portion for receiving the driving blows to be transmitted to the segment to which it is applied.

Multiple-Band Embodiment-FIGS. 17 and 18 inch diameter inner band B1 may be used, surrounded in turn by a band B2 of 48-inch diameter.

Band B1, by establishing a rather firm contact between pole P2- and the soil body SBl which it encircles, has the.

described tendency to cause pole P2 to act asthough its upper imbedded portion has the larger diameter of: band B1, and the soil body SE2 encompassed and confined between the bands B1 and B2 causes the band 31 to effectively impart to the pole P2. the tilting-resistance characteristics approximating those of a pole having the still larger diameter of band B2 at the region encircled. by reinforcing bands B1 and B2.

If desired, three or more concentric bands may be employed havingband lengthsand diameters'according to the nature or resistance characteristics of thesoil, or according to the breaking strength of the pole, dependent in turn upon whether it is a wooden poleor a steel pole.

When the pole 2 is of steel construction, and is imbedded in a hardsoil, bands B-1 and B'Zmay be employed of the approximate dimensions given if the steel pole itself is of the assumed IO-inch diameter. If the steel pole is ofsubstantially smaller diameter, it may be found desirable to encircle the pole with an inner band (not shown) having a nominal diameter about twice that of the steel-pole toprovide an effective enlarged soil grippingsomewhat lessthan the pole diameter. For softersoilsexhibiting a tendency to-separate in frontofa pole. under tipping pressureand to reform behind it within the reinforcing band, that tendency usually disappears when thedistanoe frompoleto band isreduced to no more than one-half the diameter of the pole.

It will beobserved that the concentric bands B1" and- B2 OfAFIGS. L7. and 18 areeach illustrated as comprising-- but two segments S having edge formations: similar to those of segment S4 of'FIGS. 12 to 14 and held together For by a pair of joining clips 49 in the manner indicated in FIG; 14. They are so illustrated for soil conditions permitting a band to be driven into the soil as a unit, as by applying a heavy weight rather symmetrically around the assembled band and supplying band-sinking vibrations to the weight structure, as at a frequency of about 1200 cycles, which technique is known in connection withpile-driving operations.

It will-be understood, of course, that the bands B1 and B2 may each be of the: multiple sectioned construction according to any of the segments S to S4 of FIGS. 1 to 14 when they are to be driven into position in the segment-by-segment fashion described.

While- I have described above the principles of my invention in. connection with specific apparatus, it is to be clearly understood that this description is made only by way of example and not as a lirnitationto the scope of the invention.

I claim:

1. A method of plan-ting a post in cohesive soil to project therefrom along a reference axis which is to be stabilized against tipping, said method consisting in utilizing a selected annulus of the existing soil as a virtual solid extension of the. adjacent. portion of the pole and including the steps of forming a hole in the soil along said axis to a maximumcross section slightly greater than the end of a post to be received therein, inserting the lower end said wall such that the post end, the confining-wall, and

the soil therebetween functions a virtually solid body in resisting-lateral tipping pressures.

2-. A method of planting a post. in cohesive soil topr ojectutherefrom along a reference axis which is to be stabilized against tipping, said method consisting in. utilizing a selected annulus of the existing soil as a virtual'solid extension of the adjacent portion of the pole and consisting of the single step of: inserting retainer sleeve structure into said soil in a direction parallel, to said axis to provide an endless wall encircling said axis along a path spaced transversely from said post. to provide a soil-confining wall thatretains an annulus ofsoil having an outer diameter in the range of from about, one and one-half to about three times the thickness of the post compacted between said post and said wall such that the post end; the confining wall, and. the soil therebetween function as a virtually solid body'in resisting lateral tipping pressures.

References'Cited inthefile of this patent UNITEDSTATES PATENTS 313,830 Meigs Mar. 10; 1885 735,489 Friestedt Aug. 4, 1903 1,244,119 Mulnix- Oct. 23, 1917 1,784,770 Wiley; Dec. 9, 1930 1,841,759 Nolte Ian. 12, 1932' 1,868,494 Collins July 26, 1932 1,971,615 Marter Aug. 28, 1934 2,308,793 Upton Jan. 19, 1943 FOREIGN PATENTS 966,350 Germany -g July 25, 1957 i a u- 

2. A METHOD OF PLANTING A POST IN COHESIVE SOIL TO PROJECT THEREFROM ALONG A REFERENCE AXIS WHICH IS TO BE STABILIZED AGAINST TIPPING, SAID METHOD CONSISTING IN UTILIZING A SELECTED ANNULUS OF THE EXISTING SOIL AS A VIRTUAL SOLID EXTENSION OF THE ADJACENT PORTION OF THE POLE AND CONSISTING OF THE SINGLE STEP OF INSERTING RETAINER SLEEVE STRUCTURE INTO SAID SOIL IN A DIRECTION PARALLEL TO SAID AXIS TO PROVIDE AN ENDLESS WALL ENCIRCLING SAID AXIS ALONG A PATH SPACED TRANSVERSELY FROM SAID POST TO PROVIDE A SOIL-CONFINING WALL THAT RETAINS AN ANNULUS OF SOIL HAVING AN OUTER DIAMETER IN THE RANGE OF FROM ABOUT ONE AND ONE-HALF TO ABOUT THREE TIMES THE THICKNESS OF THE POST COMPACTED BETWEEN SAID POST AND SAID WALL SUCH THAT THE POST END, THE CONFINING WALL, AND THE SOIL THEREBETWEEN FUNCTION AS A VIRTUALLY SOLID BODY IN RESISTING LATERAL TIPPING PRESSURES. 